1. Field of Invention
The present invention relates to locking and unlocking devices of a rotary nature whereby two members that are rotatable about a hub can be adjustably fixed in a variety of positions by the deployment of cog type teeth or locking pins.
2. Description of the Prior Art
There are numerous examples of rotary locking devices which provide the rotatable members to be adjustably fixed in a proscribed position and then unlocked to allow movement into another fixed position. These devices usually provide a locked position by using pins or gears and are subsequently unlocked by disengaging the pins or gears by depressing a spring loaded mechanism which when released causes the pins or teeth of the gears to engage their female counterpart thereby allowing the rotatable members to be repositioned in another locked position. There are many examples of such pin and cog designed devices.
U.S. Pat. No. 5,689,999 issued to Wiley, Gay, and Larkin Nov. 25, 1997 for an Adjustable Rotary Locking and Unlocking Apparatus. This example of such a device has a plurality of spring loaded pins in a hub that engage one at a time into a similarly sized plurality of holes spaced around the axis of another hub. The draw back of this design is that only one pin engages at a time thereby diminishing the strength of the locking device. Also, to achieve small increments of angulation of the two rotatable members requires a greater plurality of pins and holes, thereby increasing the cost and complexity of the device.
U.S. Pat. No. 5,056,805 issued to Chia-Ho Wang Oct. 15, 1991 for a Baby Stroller demonstrates a multipositional locking hub device that allows for the handle of the stroller the ability to be locked in a plurality of positions to accommodate more comfortable settings of the handles while pushing the stroller. This is achieved by allowing the mateable members to pivot around the hub mechanism through an arrangement of several interlocking gears, which are held in place by the tension of a single spring. The use of three gears with interlocking teeth allows for shearing force to come into play as the two primary external gears are offset by the intermediary gear.
U.S. Pat. No. 5,279,387 issued Jan. 18, 1994 to Swiderski and Seadler for an Articulated Ladder Assembly. The Swiderski and Seadler invention utilizes pivotable hubs that lock and unlock to angularly adjust the segmented ladder sections into different folded or extended configurations. This variability of positions is provided by the usage of interlocking teeth on the flat surface of round hubs held in tension by the use of a single coil spring in conjunction with a single disk spring. This locking hub mechanism does not allow for fine angular variations of locked settings.
What is needed is an adjustable rotary locking and unlocking device that is designed to have greater strength and greater range of angular variability in the locked mode with pushbutton ease of operation.